Process for distilling oils



April 17, 1928.

A. E; HARNSBERGER PROCESS FOR DISTILLING oILs Filed NOV. l2, 1926Patented Apr. 17, 1928.

APATENT OFFICE.

AUDLEY E. HARNSBERGER, OF COLUMBUS omo, AssIGNon To THE PURE 01T. com-PANY, OF CHICAGO, ILLINOIS, A CORPORATION 0F OHIO.

l PROCESS FOR DISTILLING OILS.

Application lc-d November 12,1926. Serial No. 148,060.

This invention relates to a new and improved process for eii'ecting acontinuous distillation of mineral oil or petroleum under substantiallyvacuum conditions, whereby the oil under treatment is separated into twoor more fractions. Dist-illation f under vacuum conditions is offundamental uum, so

importance in preventing the cracking or molecular decomposition ofcertain hydrocarbons which ldestroy .the viscosity and color of the oil.Distillation can be carried on when a vacuum is present at aconsiderably lower temperature than. when ordinary atmospheric pressuresor superatmospheric pressures are employed, and distillation at or aboveatmospheric pressure requires ordinarily such high temperatures that thecracking of the oil is apt to occur, suchhigh temperatures frequentlyresulting in depriving the oil of its' desired color and viscousproperties. Again, distillation under vacuum has the advantage ofovercoming this tendency toward cracking because of the -fact that lowertemperatures may lbe utilized, but in prior apparatus and methods, ofwhich I now have knowledge, the apparatus has been costly to install andexpensive and difficult to regulate and operate, and it is, therefore,an outstanding object of the present invention to tem of distillation ofsimple yet efficient form and wherein investment and operating costs maybe maintained at a comparatively low level.

Another object of the invention resides in the provision of distillingapparatus formed to include a primary oil heater in the form of acontinuous pipe coil wherein the latter is of such form that the vacuumpresent in the system will penetrate back to the point of introductionof the oil into the coil,`or to such other location wherein the oilwould be subjected possibly to dangerous overheating were the vacuum notpresent, the design of the coilxbeing su v,h that by enlarging theinternal diameter thereof. either continuously or intermittently, atvarious points throughout the length thereof the friction loss of theoil,passing be such -as to allow the vacuum the coil or tube bank oilapproaches cracking temperature.

to penetrate The higher temperature` the oil obtains in the` the greaterwill be the vacheater where primary that at the polni' of outlet,

provide a vacuum sys-v through the coil, will to a point where thev theoil temperature is the highest, the vacuum will be the greatest. Thisconstruction of the coil .or the tube bank in the primary heater orstill is one of the fundamental features of this invention, sinceexperience has shown that when oil in tube stills vaporizes, very greatback pressures are formed due to the vaporization of the oil, unlessincreased area is provided to take care of the vapor volume.

My invention vision of a process vacuum conditions, wherein theconstruction of the apparatus employed is such as to permit the vacuumto penetrate to a point below that where the temperatures aresuiiiciently.high to bring about the decomposition of the hydro-carbonwere. the vacuum conditions not present. This result being attainedprimarily in this instance by the variations in the cross-sectionaldiameter of therefore consists in the prothe coils or tubes constitutingthe primary heater or still. I

The invention further consistsv in a vacuum system of oil distillationwherein a primaryheating element of improved eiiiciency is providedpermitting the system to operate under lower temperatures than thoseused in present systems with consequent saving in the vamount of fuelrequired and also in generally simplifying and reducing the amount ofapparatus required in carrying out the system.

For a further understanding of my invention reference is to bedescription wherein further features and objects ofthe invention will bein part described and in part obvious, reference being had to theaccompanying drawing wherein:

Figure 1 represents diagrammatically theapparatus which may be employedfor carrying out the invention. l

Figure 2 is a detail view on an enlarged scale ofthe primary heatingcoil.

Figure 3 is a similar view of a modiiied form thereof.

Referring now to the drawings wherein I have illustrated more or lessdiagrammatically one form of apparatus which can be successfullyemployed to carry out the invention, and wherein the reference numeral 1designates the setting of a primary heater of the: type commonly knownas a tube still. This heater includes the usual combustion chamber 2 anda tube chamber 3,

for distilling oil under' hadA to the following the chambers 2 and 3being separated by means of a bridge wall 4. Within the chamber 3 areupper` and lower tube banks 5 and 6 respectively, and the lower bank hasconnected therewith a supply pipe 7, leading from a source of oilsupply,and through which pipe the cold or preheated oil is pumped to theheater. After circulating through the lower bank of tubes thetemperature of the oil is raised, for example, from atmospheric tosubstantially 600 degrees F., wherein the lighter fractions of the oilare allowed to readily vapo1ize,witl1 out danger cf cracking theunvaporized portion of the oil. and pass from the heater by way of anoutlet pipe 9 which leads to a vapor chamber 10 provided in a. vaporizer11. The gases and vapors generated by this initial heat-ing step passupwardly through the separator and are preferably passed through acooling coil 12a, Where the vapors are reduced to liquid form andsuitably stored for future use.

The heavier or unvaporized fractions of the oil collect in the bottom ofthe separator and are removed therefrom by Way of a pipe line 13, inwhich is situated a pump 14 of any suitable type. This condensate isthen forced through the line 14 to the inlet side of the upper tube bank5, where the oil is subjected to the higher temperatures prevailing inthe tube still or primary heater, but wherein provision is made in theconstruction and form of the coil comprising the upper bank 5 to preventthe decomposi tion or cracking of the oil.

As an illustration of a specific form which the upper bank of tubes maytake, it is calculated that the tube bank 5 having tubes of one inchinternal diameter at` `the point Where the oil enters, that is, at thebottom of the bank, should have approximately tubes of six inchesinternal diameter at the oil exit, or at the upper end of the bank,stepping up the sizes at intermediate points in the bank. The increasein diameter `may be of a gradual tapered form, as shown in Figure 2ormay be of an intermittent, ab-

- ruptly stepped form as shown in Figure 3.

The preferred method is to increase the diameter of the individual tubescomprising the upper bank successively in an upward direction. B v thisconstruction the design of the still will be such that by theenlargement of the tube diameters at variousvpoints in the still,friction loss of the oil passing through the tubes will be such as toallow the vacuum to penetra-te the tube bank toa point Where the oilapproaches cracking temperatures.A It is believed'that without theenlargement of areal as the oil progresses through the tube bank,highest etliciency would not be obtained from a vacuum tube .tilL sincethe oil being under pressure could not vaporize except at a hightemperature,

bank as disclosed resides in the fact that experience has shown thatwhen oil in tube stills vaporizes, very great back pressures are formeddue to the vaporization of the oil, and the increased area is providedto take care of the vapor volume and to allow for its proper circulationbank without local overheating.

The increasing pipe area from the inlet to the out-let end of the pipestill 5 is suiiicient so that by the resulting decrease of pipe frictionor back pressures of oil traveling in the still, four inches of mercuryabsolute of vacuum on the outlet of the still will penetrate to the`inletof the still, the above-mentioned vacuum reducing gradually towardthe inlet end of the still. For example, it has been found that theprocess will produceunusual distillates such as of cylinder stock gradehaving a Baume gravity of 20.3 and a viscosity in excess of 150 secondsSaybolt Fah.) with a flash test of 560 Fah. and a fire test-of 625Fahand of good color vvhen operating with a vacuum of 1.75 inches ofmercury absolute on the outlet of the still, and showing 12 inches ofmercury ab- 'solute on the inlet side, the temperature of the outlet oilbeing 690 Fah. Various lighter distillates can be produced by reductionin the outlet temperature of the still, these latter distillates showingsuperior yields, color, Hash and fire tests than those produced byordinary methods.

The oil having been brought up to the dcsired temperature in the stillis discharged through the tube y from the upper bank 5 of the tubes andisv conducted through t-he vapor line 15 to a vapor chamber 16 providedin a separator 17. In the particular form of the invention illustratedthe heavier fractions are collected in liquid form inthe bottom of theseparator and are permitted to pass through a cooling coil 18 andremoved from the still by a condensate pump4 19, which may be of thecentrifugal or direct acting type, either steam orI electric driven.

To further f fractionate the discharged vapors, the top of the separator17 is provided With a scrubber or dephlegmator 20, in which the vaporsare scrubbed and then passed through the vapor line 21 to a secondseparator 22. which includes the usual separating chamber 23 and asuperposed scrubber 24. The bottom of the separator 22 lrater 29. Thecoil 30 is connected with a condenser and a discharge pump 26 by meansofa pipe line 27 through which the condensate formed in the separator 22is circulated. The vapors present in the hydrocarbons led to theseparator 22 are permitted to pass to the scrubber 24 and thence by wayof a pipe line 28 =to a third separator 29, in which is provided acooling or refluxing coil 30., through which cold oil may be circulatedso as to eifect the condensing of the vapors within the sepaextends alsoto a similar coil 31 arranged in the Asecond separator 22, and from thiscoil a pipe line 32 extends to the pipe line entering the tube bank 6.It will be apparent that by the provision of suitable valves the flow ofoil through t-he coils and 31 may be readily regulated so as to controlthe heat exchanging operation thereof in the separators 22 and 29. Thefinal condensate collected in the separator 29 is led through acondenser 33 to a. pump S4 which may be of'the types indicated at 19 and26. Additional cooling coils 29b and 29C are provided in the separator29 to insure final condensation, through which may be circulated oil,water or brine.

The vacuum in the system may be governed by means of a vacuum pump 35,which communicates with the chamber 29 by way of a pipe 36, the 'latterhaving at its inlet end the coil 29, through which a cold liquid will becirculated to provide maximum cooling of non-condensable vapors: formedduring the operation. It will be understood that as many of thefractionating separators may be provided in the system as desireddepending upon the number of' cuts or fractions wanted and that thespecific form and arrangement of the fractionating equipment lmay bevaried from that herein conventionally illustrated Without departingfrom the principles of the invention. Any non-condens-able vapors whichmay be formed in the operation of the system will be removed by means ofthe vacuum pump 35, which may be of the displacement type, hurling watertype or steam ejected. The pump 35 thus serves to place theA entiresystem under vacuum conditions as far back as tlie inlet end of the tubebank 5. v

lt will he seen that by the present invention a vacuum system of oildistillation is provided b v which the operating temperalures may bemaintained at safe levels to prevent the cracking or moleculardecomposition of the oils handled by the system.

The system thus produces distillates of im proved viscosity and color,particularly well adapted for use 1n the formation and production oflubricating oils. I 'am aware that the general advantages accruing fromvacuum distillation systems have been recognized and in a measuredeveloped by prior patentees, however, to the best of my knowledge suchprior systems have never employed the principle of extending the vacuumback to the point of introduction of the oil into the lprimary heater orto such positions Where the temperatures employed might have the eEectof cracking the-oil were the vacuum not present.

Iiurthermore, the use of a tube type of heater, instead of a shell ordrum type,rhas the advantage that the oil exposed to hot metal travelsat high velocities; increasing heat transfer and minimizes to a greateX- tent the likelihood of local overheating due to the turbulent flow.This is also accomplished Without the use of steam, thereby reducingthroughout the system the size of vapor lines, containers and otherfractionating equipment necessary per unit of capacity. Also it is wellknown that tube heaters can be operated with greater fuel economy thanthe shell or ldrum type heaters. Again. by employing the tube type ofprimary heater the vapor pressures will be reduced on the oil circulatedtherethrough, as compared with the drum or shell type of heater, by theelimination of the hydrostatic head. This head, in a drum or shell typeof still, causes pressure on the oil at the bottom of the container andthereby renders the vacuum less effective.

What is claimed is:

l. The method of vacuum distillation of mineral oil, which consists indrawing a qu'ant1ty of oil without reduction in its total weight througha heated pipe still of progressively increasing cross-sectional pipearea from the inlet to the outlet ends thereof, said increasing pipearea permitting such reduction in ba'ck pressure due to pipe friction ofthe oil and vapors drawn through the still to allow a vacuum carried onthe outlet end of the still to penetrate back to the inlet end thereof.

2. The method of vacuum distillation of mineral oil, which consists indrawing a quantity of oil Without reduction in its total weight througha heated pipe still of progressively increasing cross-sectional pipearea fromthe inlet to the outlet ends thereof, said mereasing pipe areapermitting s'uclrreduction in back pressure due to pipe friction of theoil and vapors drawn through the still to allow a'vacuum carried on theoutlet end of the stillto penetrate back to the inlet end thereof, saidvacuum being sufliciently high to permit vaporization of the 'oil1 ltotake place in the heating zones of the sti outlet ends thereof, saidincreasing pipel area permitting suehreduction in back-pressure'of theoil and .vapors drawn through a The method of distini'ng minerai Oil,A

the still to allow a vacuum carried on the.

out et end of the still to penetrate back to the inlet end thereof, theYoil being dra-Wn through said still at progressively increasingvelocities as said oil reaches zones 0f higher temperature as a resultof vaporization of the oil within the heating zonesof the still.

4 The method of distilling mineral oil,-

which consists in the step of drawing a quantity of oil through a heatedpipe stilllpossessing a progressively increasing pipe area from the oilinlet to the oil outlet ends thereof, said increasing pipe areapermitting such reduction in back pressure on the oils yand vapors drawnthrough the still to allow a .Vacuum carried on the outlet end of thestill to penetrate back to the inlet end thereof, said vacuum beingsufficiently high to permit vaporization of the yoil to take place inthe heating zones of the still, the temperature of the oil and vaporspassing through the still being prevented from exceeding the temperatureof the oil and vapors issuing from the outlet- .of the still.

In testimony whereof I affix my signature.

AUDLEY E. HARNSBEBGER.

